From 56458cb168bf79ae51ba1efc3acec15874cc34a9 Mon Sep 17 00:00:00 2001 From: Nanley Chery Date: Thu, 11 May 2017 15:57:59 -0700 Subject: [PATCH] anv/formats: Update the three-channel BC1 mappings The procedure for decompressing an opaque BC1 Vulkan format is dependant on the comparison of two colors stored in the first 32 bits of the compressed block. Here's the specified OpenGL (and Vulkan) behavior for reference: The RGB color for a texel at location (x,y) in the block is given by: RGB0, if color0 > color1 and code(x,y) == 0 RGB1, if color0 > color1 and code(x,y) == 1 (2*RGB0+RGB1)/3, if color0 > color1 and code(x,y) == 2 (RGB0+2*RGB1)/3, if color0 > color1 and code(x,y) == 3 RGB0, if color0 <= color1 and code(x,y) == 0 RGB1, if color0 <= color1 and code(x,y) == 1 (RGB0+RGB1)/2, if color0 <= color1 and code(x,y) == 2 BLACK, if color0 <= color1 and code(x,y) == 3 The sampling operation performed on an opaque DXT1 Intel format essentially hard-codes the comparison result of the two colors as color0 > color1. This means that the behavior is incompatible with OpenGL and Vulkan. This is stated in the SKL PRM, Vol 5: Memory Views: Opaque Textures (DXT1_RGB) Texture format DXT1_RGB is identical to DXT1, with the exception that the One-bit Alpha encoding is removed. Color 0 and Color 1 are not compared, and the resulting texel color is derived strictly from the Opaque Color Encoding. The alpha channel defaults to 1.0. Programming Note Context: Opaque Textures (DXT1_RGB) The behavior of this format is not compliant with the OGL spec. The opaque and non-opaque BC1 Vulkan formats are specified to be decoded in exactly the same way except the BLACK value must have a transparent alpha channel in the latter. Use the four-channel BC1 Intel formats with the alpha set to 1 to provide the behavior required by the spec. v2 (Kenneth Graunke): - Provide a more detailed commit message. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100925 Cc: Reviewed-by: Kenneth Graunke Reviewed-by: Jason Ekstrand Signed-off-by: Nanley Chery --- src/intel/vulkan/anv_formats.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/intel/vulkan/anv_formats.c b/src/intel/vulkan/anv_formats.c index c39cec3800a..25801e8b065 100644 --- a/src/intel/vulkan/anv_formats.c +++ b/src/intel/vulkan/anv_formats.c @@ -179,8 +179,8 @@ static const struct anv_format anv_formats[] = { fmt(VK_FORMAT_D24_UNORM_S8_UINT, ISL_FORMAT_R24_UNORM_X8_TYPELESS), fmt(VK_FORMAT_D32_SFLOAT_S8_UINT, ISL_FORMAT_R32_FLOAT), - fmt(VK_FORMAT_BC1_RGB_UNORM_BLOCK, ISL_FORMAT_DXT1_RGB), - fmt(VK_FORMAT_BC1_RGB_SRGB_BLOCK, ISL_FORMAT_DXT1_RGB_SRGB), + swiz_fmt(VK_FORMAT_BC1_RGB_UNORM_BLOCK, ISL_FORMAT_BC1_UNORM, RGB1), + swiz_fmt(VK_FORMAT_BC1_RGB_SRGB_BLOCK, ISL_FORMAT_BC1_UNORM_SRGB, RGB1), fmt(VK_FORMAT_BC1_RGBA_UNORM_BLOCK, ISL_FORMAT_BC1_UNORM), fmt(VK_FORMAT_BC1_RGBA_SRGB_BLOCK, ISL_FORMAT_BC1_UNORM_SRGB), fmt(VK_FORMAT_BC2_UNORM_BLOCK, ISL_FORMAT_BC2_UNORM),